Preheat the oven to 180 degrees Celsius. In a large bowl add chocolate and butter. Microwave them for 30 seconds. Take the bowl out, stir and again microwave for 30 seconds. Repeat this until the mixture is smooth.
After the chocolate melts, add sugar, eggs, a pinch of salt and mix well. Now add the flour and combine well with the mixture in the bowl. See that no lumps are formed.
Pour the batter into a greased dish or baking tray and bake for 25 minutes or till the centre of the brownies are cooked. Take out the brownies from the oven and add a layer of marshmallows on top of the brownies.
Bake the brownies again for 3-4 minutes or till the marshmallows puff a little. Now, take out the brownies and let them cool down.
Cut the brownies into pieces and serve warm. Enjoy!